1. Field of the Invention
The present invention relates to an engine control apparatus and particularly to an engine control apparatus that raises the reliability of a gearshift position signal obtained from a gearshift sensor so that an engine can more safely be started.
2. Description of the Related Art
A vehicle engine is not configured in such a simple manner that just closing the starting switch makes the starter motor rotate to start the engine; the engine is started through close relationship with an engine control apparatus that incorporates a microprocessor.
The foregoing engine control apparatus reads an identification code given to an engine starting operation key so as to perform control related to prevention of vehicle theft utilizing an operation key in an improper manner. Additionally, in cold regions, the engine control apparatus may perform control related to remote starting of an engine by a wireless signal instead of an engine starting operation key. Furthermore, the foregoing engine control apparatus may be utilized to perform control in which, for the purpose of energy-saving driving, when a first appropriate condition is satisfied, supply of the fuel is automatically interrupted to stop the engine, and when a second appropriate condition is satisfied, the engine is automatically restarted.
In these diverse methods for starting control, it is important to determine whether or not there has been selected a vehicle-transmission setting position at which the vehicle cannot be driven. Specifically, in the case of an automatic transmission, when the gearshift lever is in the neutral position or the parking position, the vehicle cannot be driven; additionally, in the case of a manual transmission, when the gearshift lever is in the neutral position, the vehicle cannot be driven.
Accordingly, after a signal from a gearshift sensor is inputted to a microprocessor and it is ascertained that the gearshift lever is in the neutral position or in the parking position, the engine is allowed to be started.
For example, in an apparatus disclosed in Patent Document 1, as a requirement for automatic restarting of an engine, a neutral switch signal from the transmission is applied. Additionally, in an apparatus disclosed in Patent Document 2, by determining whether or not the gearshift of a transmission is in a position where the vehicle cannot travel, remote starting is allowed. Additionally, in an apparatus disclosed in Patent Document 3, even in the case of direct starting through a starting switch, there is utilized a neutral switch signal as a requirement for starting.
On the other hand, in a bad environment where a vehicle battery as a power source for a starter motor is not sufficiently charged and the ambient temperature is low, in the case where there occurs an emergent situation in which, due to an excessive load current at a time immediately after the drive of the starter motor is initiated, the voltage of the vehicle battery is abnormally lowered and hence an engine control apparatus cannot be operated, there is required a means that backs up the engine control apparatus in such a way that the operation of the starter motor is continued without relying on the engine control apparatus, the load current is decreased and hence the voltage of the vehicle battery recovers, and then the operation of the engine control apparatus is resumed. For example, for an apparatus disclosed in Patent Document 4, there has been disclosed a means that allows an engine to be started even in the case where there exists no authentication approving determination for preventing a theft, and then in the case where the result of an authentication determination becomes “unallowable”, starting control and ignition control are stopped. However, in the apparatus disclosed in Patent Document 4, the behavior of the gearshift sensor is not described.
In each of the foregoing apparatuses disclosed in Patent Documents described above, a plurality of fixed contacts corresponding to gearshift positions, a variable resistor, a non-contact linear sensor, or the like is utilized as a gearshift sensor. For example, in an apparatus disclosed in Patent Document 5, by utilizing a plurality of fixed contacts corresponding to gearshift positions and resistor circuitry, a gearshift sensor equivalent to a variable resistor is configured so as to generate output voltages corresponding to gearshift positions that are inputted to a microprocessor via an AD converter provided in a control apparatus for an internal combustion engine. Additionally, in Patent Document 6, there is provided a non-contact magnetic sensor that generates signal voltages corresponding to the shift positions of a gearshift lever.